Analysts cite a pull back in valuation and new ad formatting as a reason for the upgrade. Still, Cantor Fitzgerald sees Facebook as the top stock in the sector.

"To be sure, we still favor Facebook, which is a 2014 top pick for us; that said, a combination of a positive read into 1Q 2014 results, the imminent launch of several new ad formats to drive monetization, and a pullback in valuation make us less negative on the name," Cantor Fitzgerald said.

"Given its ~100% annual revenue growth, Twitter remains positioned as an ideal play on continued secular growth in mobile and social ad spending, particularly as high-value brand ad dollars transition to the Internet," the note continued.